Metallurgical filter and article therefor



April 21, 1931. E. R, CRUTCHER E'r AL 1,801,652

METALLURGICAL FILTER AND ARTICLE THEREFOR Filed Aug. 5l. 1929 3Sheets-Sheet l @eA/Mad ATTORNEY April 21, 1931- E. R. cRUTcHER E'r A1.1,81662 METALLURGICAL FILTER AND ARTICLE THEREFOR Filed Aug. 3l, 1929 3Sheets-Sheet 2 INVENTOR FUI-atelier Patented Apr. 21, 1931 ,UNITEDlSTATES PATENT OFFICE ERNEST n. environne, Aiiirfurncwr WALTMA'N, AND4WALLME e. wooLF, oF KELLOGG,

v Inmo METALLURGICAL FILTER AN D ARTICLE THEREFOB Application AfiledAugust 31, 1929. Serial No. 389,744.

This invention relates to improvements in rotary filtering mechanismwhich 1s primarily intended for use in the metallurgicalv art and whichisv more specifically *designedand adapted for the recovery ,of zincsolution from mineral ore pulp, although its utility is not whollylimited to the performance of this function.

In this type of slowly revolving filter, the pulp is maintained at arelatively high temperature and filtering is accomplished by amotivating agent or. means which may be either suction or internalpressure, and the filtering structure, with .which the usual filtervrotatable cylinder is equipped, cornprises a series of channelledfiltermembers and a filter cloth. l

Itis a feature of this invention to provide a novel filtering structurewhich is sov constructed and shaped as topuesent to the pulp a verygreatly increased lteringlarea, compared to what has heretofore beenpossible, without enlarging the filter cylinder either diametrically orlongitudinally.

More specifically speaking, this feature is consummated by a novel formof filtering member or bar which is provided with a cross section thatresults in the'filtering area assuming a widely sloping and transverselydivergent hill and vale or undulatin contour which performs the dualfunction of' relatively enlargingthe filtering area and more effectivelyagitating, lifting and'discharging the pulp as the hill and valefiltering area passes-through and ascends above the pulp.

A further feature consists in a novel manner and means of disposition ofthe filtering cloth, with which'the channelled' bars are faced;whereby-substantially all of the forms in one unit thereby causing theegressling solution to become muddy, such unit can be shut off withoutaffecting any of the other units. A special phase of this novel featureinvolves means for 'sealing the filtering units for egressingsegregation thereof, both longitudinally and circumferentially'of thefilter.

As a direct result of the novel features of anchoring the filteringcloth, the filter avoiding the necessity of removing said bars when anew filtering cloth is installed.

The improved filter structure is also addressed to a novel means fordischarging the filtered solution which involves chambering the filterbars along their radially inner apices or vertices in such a manner asto afford discharge of-the solution and not inerrupt-the cross sectionalcontinuity of -said ars.

The invention comprises an improvement in the filter mechanism, as acombinative entity, and also to novell features of the filter bars asanv article of manufacture, and the invention will be more fullydescribed in connection with the accompanying drawings and will be moreparticularly pointed out in and by, the appended claims.

In the drawings Fig. 1, is a view in elevation of a metallurgicalfilter-for which the device of this invention is primarily intended.

Fig. 2, is a sectional view on line 2-2 ofm Fig. 1, showing the cylinderon a relatively enlarged scale and illustrating the application theretoof the device of this invention.

Fig. 3, is a sectional view on line 3 3 of Fig. 4, illustrating thenovel means whereby gmx ` through the for anchoring the cloth at theends of the filter bars.

Fig. 6, is an enlarged fragmentary sectional view of two adjacent filterbars and illustrating the manner in which the filtering cloth isanchored circumferentially of the filter.

Fig. 7, is a sectional view on a reduced scale of one of the filter barsand is taken on line 7-7 of Fig. 8.

Fi 8, is a sectional view on line 8-8 of Fig.

Fig. 9, is a sectional view on line 9-9 of Fig. 5, the same being on areduced scale.

Like characters of reference designate similar parts throughoutthedifferent figures of the drawings.

A rotatable filter cylinder is very generally indicated at 1, the samehaving suitable tracks 2, mounted on wheels 3, and being rotated by anysuitable means about its own longitudinal axis. Any suitable means,designated as a whole at 4, may afford an axial supply of steam, and themeans of charging r the cylinder with pulp need not be considered.

Referring to Fig. 2, it will be seen that the cylinder is shown made upof an outer` casing 5, one only being shown, and that said casing islined with wood or the like, as indicated by 6, as is usual, thusreducing heat radiation. This isthe general construction employed inthis type of filter where an internal pressure medium is employed as amotivating a ent to force the solution ltering structure. The solutionthat has been filtered through the pulp is discharged at a plurality ofradial and circumferential points from the filter cylinder, and astationary jacket 7, is shown for receiving the solution from therotating cylinder, as will be presently more fully described. l

Reference will next be made to that portion of the subject matter which,in combination with the foregoing, and independently thereof,constitutes the inventive improvement.

The filter structure specificially shown, includes a .series of members,sections or bars 8, which in practice are generally made of wood andwhich are disposed in lateral juxtaposition with respect to each otheragainst the interior lining 6, of the cylinder. Said bars are disposedlongltudinally of the cylinder and in actual practice, there are twosets of bars in end to end relation, and adjacent spaced ends, which aregenerally disposed in a longitudinal central position with respect tothe cylinder, are the discharge ends, as will presently appear.

Referring now to the particular structure 'of the improved bars andespecially to Fig.

4, it will be seen that the same are of triangular cross sectionalthough it is not essential that they be either equi-lateral orequiangular. One side, designated at 9, is what will be termed a smooth`or plane side and this side 9 is disposed abreast of the concavedlinterior 10, of the filter cylinder, as shown. The linear 'vertices orapices 11,

'abut against the cylinder wall 6 and the intermediate plane surface orside 9 is in spaced relation therewith. The remaining sides 12,extending from vertices 1l to vertex 13, are the functioning sides ofthe bar 8, which may be termed the filter sides or faces, andthe sameare provided, each with a series of longitudinally disposed channels 14for conveying the filtered solution, which is in this case, the zincsolution, and hence these channels may be termed filter channels. Itwill be noted that these bars present 'a continuous undulating hill andvale contour with the hills sloping in widely divergent relationtransversely of the bars.

These bars 8, all of which are identical in structure and function, andonly 4one of which need be described in detail, are disposed completelyabout the internalcircumference ofthe cylinder 1, as shown in Fig. 2,and these bars constitute one portion of the filter structure.

The remaining portion of the filter structure is formed by a-flter cloth15 which is usually of a canvas yhaving the required or desired opennessof texture for the materials being filtered. Heretofore, the filter barsor like integers have been enclosed by the filter cloth, the latterbeing formed into an envelope to receive such integer, and hence onlythat portion of the cloth presented to the pulp has been active, andfurther, each integer and its cloth were entirely separate and distinctfrom the remaining integers.

Now it is a feature of this invention to effect a very material savingin the amount of filter cloth employed, in fact, by means of thisimproved disposition of the cloth, a greatly increased filter area canbe presented with a greatly reduced amount of cloth, in addition tomanyv other advantages of a more incidental nature.

As shown, a single sheet of cloth 15 may be extended longitudinallyy andcircumferentially of the interior of the cylinder abreast of thel activefaces of a plurality of bars 8, and hence, instead of only a portion ofthe filter cloth being active, all but the merest moiety at anchoragelines, is in full functioning disposition to the pulp. In fact, if asingle integral cylinder of such cloth could be woven, such a cloth bodycould advantageously be employed in the present construction. Thus byreferring to Fig. 2, it will be seen that the cloth 15 eX- tends abreastof the channelled sides of each and every bar 8 without traversing theplane or blank sides 9.

As a result of the filtering operation, the

pulp tends to cake on the filter cloth and theproblem of finallyremoving the cake Would be ,considerably complicated if the filter clothwere fitted tightly on the bars. Further, chemical action` of theingredients of the pulp, and attrition'to which the cloth is subjectedduring the filtering operation, would greatly shorten the life of theVcloth if the latter were fitted tightly against the bars. The presentnovel anchorin means lends itself very readily to a loose t of the clothso that on ascending. bars the Weight I of the caked pulp will tend tofiex the cloth and pull the latter away from the bars thereby breakingup the caked pulp. When apartial vacuum is established in the cylinderthe cloth can be pulled away from the bars further to facilitatebreaking up of the caked pulp. Suction through pipe 4 may be effected toform a partial vacuum in the cylinder.

This novel anchoring means for the cloth will now be specificallydescribed.

The cloth 15 is not anchored or in any way fastened to the filteringsides or vertices of the bars 8 and is fairly loosely disposed thereon.Intermediate of adjacent. bars 8, a linear retaining or cloth holdingmember is disposed, and for mechanical convenience, this member takesthe form of a pipe 17, as indicated 'in Fig. 2 but yas more clearlyshown in Fig. 6. This pipe has the advantage of presenting to the cloth15 a rounded or cylindrical surface thereby avoid'- ing injury whichmight result from a sharp surface engagement. It will be noted thatthese pipes 17 are located in what might be termed the vales between thehills, which is a result of the novel cross section of the bars 8, aswill later be more fully explained. Of course these pipes 17inay, and infact do, in many constructions, extend the entire length of the cylinderbut they maybe in sections if desired. Further, the rounded` surfacespresented by these pipes to the 4cloth act to preserve the cloth in itsinitially installed position and prevents 'the latter from assuming anundue tautness abreast.

of one bar and a like looseness along an adjacent bar. Means such asbolts 19, ex-l tend through the pipes 17 and radially through the clothandthe cylinder, vand are suitably provided with heads and nuts 20 and21, respectively. j

The novel means4 affording abutment for the pipes 17, will next bedescribed inl detail.

The companion means v or members, of pipes 17, in anchoring the filtercloth, are in the form of sealing means which are embodied in the formof strips 22. These strips are preferably of yielding material,

such as rubber, and they arel interposed between adjacent bars 8,aslshown in Fig. 6. Said strips 22 directly take the compressive stressimposed or resulting from tightening the nuts of bolts 19, and hence itwill be seen that the anchored portions of the cloth are interposedbetween the pipes 17 and the abutment strips 22. Said strips are ofsufficie'nt thickness so that the pipes 17 will not cause the filtercloth to engage the bars 8, in fact, the pipes are small enough indialneter to prevent such engagement. As shown,

the bolts 19 pass through said strips.

In practice it is preferred to very snugly fit the strips 22 between theapices 11 of adjacent bars 8,- and this snug fit, in addition to thel'compressive action of the bolts 19 in anchoring the cloth, enables thestrips 22 to perform the additional functionof sealing the filteringunits laterally from each other, and as this structural feature of theinvention extends longitudinally of the filter, it will be termed thelongitudinal sealing means for the filter units, in contradistinction tothe circumferential sealing means, which will be later described. Atthis point it is informative to state that a filtering unit comprisesone bar 8, with its two faces 12, and the extent of filtering clothnecessary to cover the filtering faces or sides of a bar. Thus, eachbar, throughout its length, with its equipment of filtering cloth, is afiltering unit. In cases where two sets offbars are employed andAdisposed in aligned and spaced end to end relation, each bar with itscomplement of filtering cloth will still be a filtering unit.

Before ,describing the manner in which the filtering cloth is installed,reference will next be made to thenovel means for sealing the units fromeach other and anchoring the cloth circumferentially of the filter.

Referring to Figs. 5 and 9,it will be seen that the two sets of bars 8have their adjacent ends 23 disposed in spaced relation and thefiltering cloth 15 is looped radially Outwardly of the cylinder 1, intothe resulting space D, and against the lining 6. A rubber or likeyielding sealing means is provlded l'which may be inthe form of a ring24, or

segments lof a ring, adapted to extend circumferentially about theperimeter of the lining 6, as shown in Fig. 9. Meanssuch as bolts 25pass through said sealing ring and the" cylinder 1, and have heads 26and nuts 27. It is advantageous to employ a washer, whiclrmay besegmental, and ring shaped,4

- as shown at 28, and through which the bolts `disposed at each end ofthe cylinder 1l..

Bolts 31 extend through the cylinder l, the cloth 15 and ringBO, andthrough a suitable washer ring 33, and have nuts 34, whereby the partscan be tightened to form an annular seal at these ends of the bars 8which are disposed at the ends of the cylinder 1.

It will now be clear that each-filter unit is sealed both longitudinallyand circumferentially of the filter. Now assume that chemical action orattrition caused a hole to be formed at any part of the active faces ofa bar 8, which would of course permit portions of the pulp to pass intothe channels 14 and hence muddy the solution as it .passes out thenipple pipes, to be later described.- In that event, it will be clearthat only one unit would be thus affected. The corresponding nipple pipewould be plugged and the remaining units of the filter would functionwithout impairment and it would not be necessary to shut down thefilter. In an installation as shown, where two sets of bars 8 areemployed, the circumferential sealing means localizes a leak in thecanvas filtering cloth to that bar adjacent to the leak, and its end toend companion bar is not at all affected. When it is considered thatthese filter cloths are changed as often as six weeks duration theimportance of this feature will be more fully appreciated. Even ininstallations where only one set of bars is employed, thecircumferential sealing means is important and useful not only as such,but as a means for facilitating the mounting of the cloth. l It will nowbe clear that in this novel construction, the bars 8 can bepe'rmanentlysecured in place because of the novel means of mounting and removing thefilter cloth, and I have shown bars 8 anchored by means such as screws35, as illustrated in Fig. 4.

i In installing the cloth, thelatter is suitably pieced so that in widthit will exceed the length of the cylinder 1 in order to make allowancefor circumferential sealing anchorage. The length of the cloth will bein suitable excess of the internal circumference of the cylinder to bedepressed into the Vales between the hills formed by the bars 8. Onelength edge willfirst be disposed subjacent an initial pipe 17, and thenunder succeeding pipes until the initial pipe has been reached,whereupon the free len h edge will be disposed beneath said initia pipein lapped relation with the first edge. The pipes wilLof course be drawntightly against the abutments 22 and this will complete circumferentialinstallation. Then the width edges and the intermediate portion will besecured by the rings 24 and. 30, as heretol fore described, and theinstallation will have been completed. Removahneed not be described asit will be obvious from the foregoing.

In this type of filter, reliance is not placed upon filtering thesolution through the filter structure by centrifugal action, but ratherby solution motivating means, which, in the present case, is in the formof an internal pressure, preferably steam, at about forty pounds to thesquare inch. |The internal temperature is around the boiling point ofwater. Of course, the internal pressure acts upon the entire filteringarea and drives the filtered solution in the filtering' channels 14,toward the egress ends of the `filter bars 8.

It is now in order to describe that novel feature of this inventionwhereby the filtered solution is egressed through the filter structure.

In Fig. 5, the ends of opposing sets of bars 8 are designated at 23 andthese ends may be termed the discharge ends. As all of the bars 8 areequipped with identical means of egress, only one need be described indetail, reference being had to Figs. 3, 4, 5, 7 and 8.

Said bar is recessed or cut away across its linear vertex 13, and thelower wall of such recess is indicated at 37, the side walls beingdesignated at 38. A bore 39 leads from wall 37 downwardly through bar 8and opens at the plane side 9. It will be noted that this recessinterrupts the cross sectional continuity of the active portions orfaces 12 of bar 8, and hence if provision were not made to avoid thedefect, the filter cloth would obj ectionably sag into such recess.

-It is therefore a feature of this invention to provide means affordingegress of the solution through this recessed portion and preserve thecrossY sectional continuity of the bar.

As shown, a nipple pipe anchorage plate 40 is suitably fixed in saidrecess upon wall 37, thereof, and is shown provided with a threadedopening in which the threaded i11- take end 41, of a nipple pipe 42, isturned. Said pipe 42 is disposed in bore 39 and extends radiallyoutwardly through cylinder 1. From theouter ends 43, of said pipes, thesolution is discharged into the stationary annular receiver 7, having adischarge outlet 44. l

A crown structure is provided for the recessed portion which may be ofinverted V-form, the same having inclined sides 45, and a suitable apex46. This structure may be made integral with plate 40, but is shownseparate therefrom and would in practice be secured thereto. The sides45 are shown provided with holes 47 for egress of the solution fromchannels 14 into the resultant chamber B, wherefrom the solution willdischarge through the nipple pipe 42.

In Fig. 5, it will be seen that the egressing means intersects theuppermost channels 14 so that the latter can readily discharge into theopenings'47. The lower channels 14 are shown connected with the upperchannels by transverse channels 48, to faciliboard would accommodate,and in addition,

lvariation of cross section that this feature is consummated with asingle layer of strata ofsuch integers. Because of the simplicity ofmanufacture, this feature is best realized by making the bars 8triangular in -c'ross section.

The filtering sides 12, of bar 8, afford space for many more channelsthan a fiat they provide a foundation on which a greatvly increasedspread of filter cloth can be made. As this filter structure passesthrough the pulp, in the lower portion of its circular travel, itagitates the same in a most effective manner, and as the hill portionsascend, they pick up and drop the pulp so as to break up and render thelatter more susceptible to quicker filtration.

It will now be clear that the widely divergent hills not only vafford agreater spread of lter cloth, but because of these widely sloping hills,the pulpy mass not only readily enters therebetween but is the morereadily discharged therefrom, as said hills ascend above the pulp level.It vwill also be noted that these bars present relatively broad flatfaces to the pulp, which, in addition to .the divergent feature, adds tothe agitating efficiency of the structure.

This form of filter bar makes .it possible to provide relatively smallegressing chambers B, in view of the fact that the increased side areaof the crown structure affords stock for a greater number ofegressingopenings.

It will be clear that irrespective of the `cross section of the lterbars 8,-apart from that shown', that it is within the province of theinvention to make them with an increased thickness portion of suchnounced formas to present well defined. side or lateral portions on eachbar. By means of this construction, prominent" hills and vales areformed.

It is believed that the invention will be fully understood from theforegoing description and while one specific form of the -invention hasbeen shown, it is not desired to be limited thereto except for suchlimitations as the claims may import.

We claim 1. In a metallurgical flter' mechanism, a rotatable filtercylinder, a filter structure therefor including a series of filter barsadapted to be dispdsed against the interior of said cylinder and havingfiltering faces,

a yielding sealing strip between each pair of adjacent bars, lafiltering cloth extending over a plurality of the filtering faces ofsaid '70 series of bars, and forming with each bar a filter unit,l androd-like members holdingsaid filter cloth against saidvstrips tolongitudinally seal each lter unit Vfrom all other filter units, andmeans for anchoring said membersto said cylinder.

2. In a metallurgical lfter mechanism, 'a filter cylinder having afilter structure composed of a series of bars and a filter clothcovering said bars and forming with each thereof a filter unit,"anddevices extending longitudinally and circumferentially of said cylinderfor sealing said units from each other.

3. As a new and useful'article of manufacture for metallurgical lters, afilter bar` of substantially triangular cross section having one plainside, the remaining sides the linear vertex of the channelled sidesbeing cut away in intersecting relation to, said channels for egresstherefrom of the solution into said cut away'portion, and said barhaving a bore leading from said cut away portion to said plain side fordischarge of the solution.

4. As a new and useful article of manufacture for metallurgical filters,a filter bar of substantially triangular cross section having one plainside, the remaining sides each having Va series of filter channelsextending longitudinally thereof, a portion of the linear vertex of thechannelled sides being cut away in intersecting relation to saidchannels for egress therefrom of the solution into said cut awayportion, asubstantially V-shaped perforated crown plate bridging saidcut away portion to form a chamber and maintain the cross sectionalcontinuity of said bar, and a nipple pipe leading from said chamberthrough the plain side of said bar for conveying 0H the solution.

5. In a metallurgical filter, a filter cylinder vhaving sets of filterbars in spaced end to end relation, a ilter cloth covering the exposedfaces of both sets of filter bars and forming with each thereof a filterunit, and

devices sealing veach unit at its sides and' filter cylinder having afilter structureA therein comprising a series of filter bars'oftriangular cross section and one side of each next to said cylinderbeing plain and the remaining sides each having a series of channelsextending longitudinally "thereof, a lter cloth held abreast ofthe'channelled sides of said 'bar-s, each bar having its linearvertexrecessed at one portion thereof in intersecting relation to saidchannels for egress of the solution from said channels into said recess,and a perforated crown structure closing said recess to form an egresschamber and maintain the cross sectional continuity of said bar, and anipple pipe leading from' said chamber through said bar and projectingthrough said cylinder for discharge of the filtered solution.

' In Witness whereof, We have hereunto afliXed our hands.

ERNEST R. CRUTCHER.

v EMMETT WALTMAN.

WALLACE G. WOOLF.

